1. Field of the Invention
This invention relates in general to manufacture of magnetic recording heads, and more particularly to a method of depositing material into high aspect ratio.
2. Description of Related Art
People need access to an increasing amount of information in our technologically advancing society. Data storage using magnetic disk drives is well known and widely used because magnetic disk devices facilitate fast storage and access of large amounts of information. A typical disk drive is comprised of a magnetic recording medium in the form of a disk for storing information, and a magnetic read/write head for reading or writing information on the disk. The disk rotates on a spindle controlled by a drive motor and the magnetic read/write head is attached to a slider supported above the disk by an actuator arm. When the disk rotates at high speed a cushion of moving air is formed lifting the air bearing surface (ABS) of the magnetic read/write head above the surface of the disk.
As disk drive technology progresses, more data is compressed into smaller areas. Increasing data density is dependent upon read/write heads fabricated with smaller geometries capable of magnetizing or sensing the magnetization of correspondingly smaller areas on the magnetic disk. The advance in magnetic head technology has led to heads fabricated using processes similar to those used in the manufacture of semiconductor devices.
The read portion of the head is typically formed using a magnetoresistive (MR) element. This element is a layered structure with one or more layers of material exhibiting the magnetoresistive effect. The resistance of a magnetoresistive element changes when the element is in the presence of a magnetic field. Data bits are stored on the disk as small magnetized region on the disk. As the disk passes by beneath the surface of the magnetoresistive material in the read head, the resistance of the material changes and this change is sensed by the disk drive control circuitry.
The write portion of a read/write head is typically fabricated using a coil embedded in an insulator between a top and bottom magnetic layer. The magnetic layers are arranged as a magnetic circuit, with pole tips forming a magnetic gap at the air bearing surface of the head. When a data bit is to be written to the disk, the disk drive circuitry sends current through the coil creating a magnetic flux in accordance with Maxwell's equations or Ampere's law. The magnetic layers provide a path for the flux and a magnetic field generated at the pole tips magnetizes a small portion of the magnetic disk, thereby storing a data bit on the disk.
The read/write head is formed by deposition of magnetic, insulating and conductive layers using a variety of techniques. Fabrication of the write head coil requires a metallization step wherein the metallization is formed in the shape of a coil. The damascene process is a technique used for forming metallization layers in integrated circuits. Generally, the damascene process involves forming grooves or trenches in a material, and then electroplating to fill the trenches with metal. After a trench is formed, however, a seed layer must first be deposited in the trench to provide an electrically conductive path for the ensuing electrodeposition process. Metal is then deposited over the entire area so that the trench is completely filled. The damascene process used in semiconductor device fabrication requires fewer process steps compared to other metallization technologies. To achieve optimum adherence of the conductor to the sides of the trench, the seed layer deposited prior to deposition of the metal must be continuous and essentially uniform. However, in a trench with a high aspect ratio, that is, the height of the trench walls is large in comparison to the width, it is difficult to uniformly cover the sidewalls of the trench with the seed layer.
A variety of vacuum techniques have been attempted to achieve the desired seed layer coverage and uniformity for high aspect ratio features, including physical vapor deposition (PVD), ionized physical vapor deposition (IPVD), collimated PVD (CPVD) and chemical vapor deposition (CVD). PVD results in non-uniform coverage, where coverage is thicker on the bottom of the trench and thinner on the sidewalls. This results in poor filling of the metal in the trench. The CVD technique has produced more uniform coverage, however, CVD requires temperatures of up to 300 C. The magnetoresistive element in the read head degrades at high temperatures, therefore the CVD process presents problems when used to manufacture magnetic heads. IPVD and CPVD processes can be tailored to provide uniform coverage. In the absence of such tooling, IBD can be used as an alternative.
It can be seen then that there is a need for a method for uniformly depositing a seed layer into high aspect ratio features formed by the damascene process during the fabrication of a magnetic read/write head.